Disodium-5,14-dihydro-5,7,12,14-tetraazapentacene-2,9-disulfonate belongs to a class of azapentacenes known to be useful as an anticataract agent. It has been marketed under the trade names Lutrax™ and Quinax™.

Org. Lett. 2008, 10 (18), 4013-4016 discloses the synthesis of substituted dihydrotetraazapentacenes (DHTAPs) in which the 2,5-dihydroxy-p-benzoquinone is reacted with various substituted o-diaminobenzenes in alcohol (or water) to afford 2,3-dihydroxyphenazines which are reacted with an excess of substituted o-diaminobenzenes in the presence of glacial acetic acid for 24 h, yielding the corresponding substituted DHTAP derivatives. Additionally, a structural study by NMR spectroscopy showed that the conjugated π-system of the pentacyclic skeleton tautomerizes depending on the electronic effect of the substituent(s).
WO2009083532 relates to a method for the preparation of substituted dihydrotetraazapentacenes (DHTAPs), said method comprising the reaction of 2,3-dihydroxyphenazines with o-diaminobenzenes, in the presence of a catalytic amount of an acid.
WO 94/29314 discloses a process for the preparation of materials with the azapentacene core which have electro active properties as well as the use thereof. A phenylenediamine is reacted with a quinone under slightly acidic conditions at reflux.
WO 2007/066098 discloses a process for the preparation of organic acids that are used for the preparation of organic ionic-crystalline photoelectric layer, in which 2,5-dihydroxy-p-benzoquinone is reacted with o-phenylenediamine and 3,4-diaminobenzoic acid in acetic acid.
WO 2007/085810 discloses a conjugated planar heterocyclic system that is a dye with a structure based on quinoxaline or which comprises quinoxaline or a derivative thereof.
J. Mater. Chem. 2005, 15, 4894-4898, describes organic thin film transistors (OTFTs) synthesis based on amorphous films of 5,7,12,14-tetraazapentacene, as well as their improved condensation process, where they were prepared by a one-step condensation reaction between 2,5-dihydro-p-benzoquinone and o-phenylenediamine in absolute ethanol with glacial acetic acid as catalyst.
Can. J. Chem. 1987, 65, 1619-1623, teaches the chemical and electrochemical reduction of the N-heterocyclic compounds, fluorindine derivatives.
Macromolecules 1991, 24 (1), 1-10, reports studies of the structural and physicochemical properties of a model compound of ladder polyquinoxalines, 5,12-dihydro-5,7,12,14-tetraazapentacene (DHTAP), including X-ray diffraction, morphology, spectroscopy, electrochemistry, complex formation, and electrical conductivity.
Chemistry-A European Journal 2009, 15 (16), 3965-3969, describes the debate on the structure of dihydro-5,7,12,14-tetraazapentacene; both the benzenoid and the quinonoid nitrogen-containing heteropentacenes were successfully isolated and investigated on their molecular and electronic structures, molecular packing, and semiconductor properties.
Beijing Yixueyuan Xuebao 1980, 12 (4), 262-3,276 discloses a method for the synthesis of 5,12-dihydro-5,7,12,14-tetraazapentacene-2,9-disulfonate (or Phacolysine), Its active component is the intermediate 5,12-dihydro-5,7,12,14-tetraazapentanece. This intermediate is purified by recrystallization from glacial acetic acid and then sublimed under high vacuum.
Chem. Ber, 1968, 101(11), 3744-3752 discloses preparation of florindin from o-quinones and o-diaminobenzene.
GB 988,331 discloses 5,12-dihydro-5,7,12,14-tetraazapentacene sulfonic acid and its sodium and potassium salts for cataract curatives, and processes for the preparation thereof. 5,12-Dihydro-5,7,12,14-tetraazapentacene and fuming sulfuric acid or chlorosulfonic acid are reacted in the presence of mercuric oxide or mercuric sulfate to provide mono- and di-sulfonic acids of 5,12-dihydro-5,7,12,14-tetraazapentacene.
FR 1,336,438 discloses a process for the preparation of 5,12-dihydro-5,7,12,14-tetraazapentacene sulfonic acid, its alkaline salts and processes for the preparation thereof. 5,12-Dihydro-5,7,12,14-tetraazapentacene and fuming acid, sulfuric acid or chlorosulfonic acid are reacted in the presence of a mercury compound to furnish mono- and di-sulfonic acids of 5,12-dihydro-5,7,12,14-tetraazapentacene.
U.S. Pat. No. 3,257,402 discloses a process for the synthesis of 5,12-dihydro-5,7,12,14-tetraazapentacene sulfonic acids and their alkaline salts, their use as cataract curatives, and processes for the preparation thereof. 5,12-Dihydro-5,7,12,14-tetraazapentacene and fuming sulfuric acid or chlorosulfonic acid are reacted in the presence of mercury oxide or mercury sulfate as catalyst. In this way, mono- and di-sulfonic acids of 5,12-dihydro-5,7,12,14-tetraazapentacene are produced.
JP38001645 discloses preparation of potassium 5,12-dihydro-5,7,12,14-tetraazapentacene-2(or 9)-sulfonate and the potassium and sodium salts of 5,12-dihydro-5,7,12,14-tetraazapentacene-2,9-disulfonic acid.